Double-Layered Negative Electrode Suppressing Lithium Deposition
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Solution Overview
Problem
Lithium ion secondary batteries face issues with lithium deposition on the negative electrode during high-load charging, leading to decreased capacity and potential internal short-circuiting, which degrades cycle performance.
Innovation Solution
A non-aqueous electrolyte secondary battery design featuring a negative electrode with a double-layered structure, comprising a graphitic material as the first layer and a non-graphitizable carbonaceous material as the second layer, which suppresses lithium deposition and enhances lithium ion acceptability and dispersibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high-load charging is performed to shorten charge time, then productivity is improved, but lithium deposition occurs on the negative electrode causing reliability to deteriorate
Solution Approach 1:
The negative electrode is divided into two distinct layers: a first layer containing graphitic material and a second layer containing non-graphitizable carbonaceous material. This segmentation allows each layer to perform its specific function - the first layer provides high capacity while the second layer suppresses lithium deposition, thereby resolving the contradiction between fast charging and reliability.
Solution Approach 2:
The negative electrode uses a composite structure combining graphitic material and non-graphitizable carbonaceous material in layered form. This composite approach leverages the advantages of both materials - the high lithium ion acceptability of graphite and the lithium deposition suppression capability of non-graphitizable carbon - to simultaneously achieve fast charging and maintain cycle performance.
2Use of energy by moving object
If graphitic material is used as negative electrode material, then energy density is improved, but lithium deposition occurs during high-load charging causing harmful factors to increase
Solution Approach 1:
The negative electrode is segmented into two layers with distinct functions. The first layer uses graphitic material to maximize energy density, while the second layer uses non-graphitizable carbonaceous material to suppress lithium deposition. This segmentation allows both high energy density and low lithium deposition to be achieved simultaneously.
Solution Approach 2:
The second layer of non-graphitizable carbonaceous material acts as an intermediary between the electrolyte and the first graphitic layer. It mediates the lithium ion insertion process, preventing direct lithium deposition on the graphite surface while still allowing efficient lithium ion transport to maintain high energy density.
3Reliability
If non-graphitizable carbonaceous material is used to suppress lithium deposition, then reliability is improved, but packing density decreases causing productivity to deteriorate
Solution Approach 1:
The negative electrode is segmented into two layers with optimized thickness ratios. The first layer (graphitic material) provides high packing density and capacity, while the second layer (non-graphitizable carbonaceous material) suppresses lithium deposition. By optimizing the ratio of first layer to second layer thickness, both reliability and productivity are improved simultaneously.
Solution Approach 2:
Different regions of the negative electrode are assigned different functions through the layered structure. The first layer region is optimized for high capacity and packing density, while the second layer region is optimized for lithium deposition suppression. This local quality differentiation allows the electrode as a whole to achieve both high reliability and high productivity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The battery configuration effectively prevents lithium deposition under high-load charging, maintaining capacity retention and improving cycle performance by optimizing the packing density and lithium ion insertion/extraction processes.
Implementation Method 1
capable of occluding and releasing an electrode reaction substance... charging in a non-aqueous electrolyte results in electrochemical doping of lithium in the positive electrode into interlayer of carbon composing the negative electrode... allowing lithium to be undoped or extracted from the carbon interlayer
Implementation Method 2
charging in a non-aqueous electrolyte results in electrochemical doping of lithium in the positive electrode into interlayer of carbon composing the negative electrode
Data Source
AI summary
A negative electrode for a non-aqueous electrolyte secondary battery is provided. The negative electrode includes: an electro-conductive base; a first layer provided on the electro-conductive base; and a second layer provided on the first layer. The first layer includes at least a graphitic material as a negative active material. The second layer includes at least a non-graphitizable carbonaceous material as a negative active material.